I think the Frigoboat Merlin II mini smart speed board has a design flaw

[garyr]

I am about at my wits end trying to figure out what is wrong with my new Keel-cooled K50F compressor with Merlin II Smart Speed Controller. The system powers up and appears to work correctly for awhile, but after a few hours to a few days the system goes into a weird state where the compressor no longer runs and the box starts warming up even though the Merlin II green LED is blinking some number of times indicating the compressor should be running. I am at the point where I think the Merlin II has a design flaw. Here's what I’ve done:

1) I confirmed the mechanical thermostat works properly.

2) When in this weird state (green LED blinking, compressor not running, and box starting to warm up) I remove one of the thermostat connectors from the Merlin II. The green LED turns solid; when I reattach it, the green LED starts blinking, the compressor starts running, and the system again behaves normally until it enters this weird state again.

3) If I turn the thermostat all the way to zero when in this weird state, the green LED turns solid. If I then turn the thermostat to maximum, the green LED starts blinking and the compressor sometimes but not always starts running.

4) If I remove the Merlin II completely and attach the thermostat directly to the compressor controller, it works perfectly, but only at the default compressor speed.

I contacted Coastal Climate Control (where I purchased the unit) and they had me send them the Merlin II for testing. They “tested” it and said it was functioning correctly. Nevertheless, they sent me a new one. I installed the new Merlin II and the same thing happens! Thinking it could be a faulty compressor controller, I dug out my old Smart Speed Controller (the old version in a little black plastic box) and attached it to the system instead of the Merlin II. It works perfectly! I’m starting to think the Merlin II has a design flaw

Your thoughts?

[GordMay]

Greetings and welcome aboard the CF, garyr.

[skipmac]

I had a Merlin II attached for a couple of years and don't recall any problems with it. Not using now as a leak killed it and haven't yet replaced it.

[s/v Jedi]

I would expect a problem with the power supply or ground.

[Richard Kollmann]

Originally Posted by garyr

I am about at my wits end trying to figure out what is wrong with my new Keel-cooled K50F compressor with Merlin II Smart Speed Controller. The system powers up and appears to work correctly for awhile, but after a few hours to a few days the system goes into a weird state where the compressor no longer runs and the box starts warming up even though the Merlin II green LED is blinking some number of times indicating the compressor should be running. I am at the point where I think the Merlin II has a design flaw. Here's what I’ve done:

1) I confirmed the mechanical thermostat works properly.

2) When in this weird state (green LED blinking, compressor not running, and box starting to warm up) I remove one of the thermostat connectors from the Merlin II. The green LED turns solid; when I reattach it, the green LED starts blinking, the compressor starts running, and the system again behaves normally until it enters this weird state again.

3) If I turn the thermostat all the way to zero when in this weird state, the green LED turns solid. If I then turn the thermostat to maximum, the green LED starts blinking and the compressor sometimes but not always starts running.

4) If I remove the Merlin II completely and attach the thermostat directly to the compressor controller, it works perfectly, but only at the default compressor speed.

I contacted Coastal Climate Control (where I purchased the unit) and they had me send them the Merlin II for testing. They “tested” it and said it was functioning correctly. Nevertheless, they sent me a new one. I installed the new Merlin II and the same thing happens! Thinking it could be a faulty compressor controller, I dug out my old Smart Speed Controller (the old version in a little black plastic box) and attached it to the system instead of the Merlin II. It works perfectly! I’m starting to think the Merlin II has a design flaw

Your thoughts?

You need to eliminate the Danfoss control module now by either removing Merlin putting a 1500 ohm resistor in thermostat wire or putting the box speed controller back on. In ether case leave them on for a long enough time to confirm the module is not the problem. Why was the there a need in the first place to replace the box controller? I assume this thermostat was not used previously on an Adler Barbour system? Also when cooling stops was red LED flashing?

The thermostat is only an off and on switch controlling from one to five milliamps of electrical current to module switching transistor. The speed control is a timer measuring the length of each compressor cycle to set compressor speed. The speed controller should never be able to stop compressor cooling.

[garyr]

Originally Posted by Richard Kollmann

You need to eliminate the Danfoss control module now by either removing Merlin putting a 1500 ohm resistor in thermostat wire or putting the box speed controller back on. In ether case leave them on for a long enough time to confirm the module is not the problem. Why was the there a need in the first place to replace the box controller? I assume this thermostat was not used previously on an Adler Barbour system? Also when cooling stops was red LED flashing?

The thermostat is only an off and on switch controlling from one to five milliamps of electrical current to module switching transistor. The speed control is a timer measuring the length of each compressor cycle to set compressor speed. The speed controller should never be able to stop compressor cooling.

Richard,


You wrote:

"You need to eliminate the Danfoss control module now by either removing Merlin putting a 1500 ohm resistor in thermostat wire or putting the box speed controller back on."

I removed the Merlin II and attached the thermostat directly to the Danfoss control module. It worked perfectly. I attached the old Smart Speed Controller and it worked perfectly.



You wrote:

"Why was the there a need in the first place to replace the box controller?

I destroyed my old compressor by running it while the boat was on the hard. When replacing it, I decided to upgrade everything and bought a new mechanical thermostat and speed controller for nominal cost.



You wrote:

"I assume this thermostat was not used previously on an Adler Barbour system?"

No. Brand new Frigoboat thermostat.


You wrote:

"Also when cooling stops was red LED flashing."

No. Just green LED flashing some number of times (sometimes one, two, three, four, five, or six flashes), but the compressor was not running.



Your wrote:

"The speed controller should never be able to stop compressor cooling."

My understanding is that when the thermostat reaches it's target temperature and the switch inside it opens, the green LED turns solid on and the compressor is "idle". When the temperature exceeds the thermostat setting, the switch closes and the green LED starts flashing some number of times indicating the speed at which it is directing the compressor controller to operate the compressor. Am I wrong?

[Richard Kollmann]

Originally Posted by garyr

Richard,


You wrote:

"You need to eliminate the Danfoss control module now by either removing Merlin putting a 1500 ohm resistor in thermostat wire or putting the box speed controller back on."

I removed the Merlin II and attached the thermostat directly to the Danfoss control module. It worked perfectly. I attached the old Smart Speed Controller and it worked perfectly.



You wrote:

"Why was the there a need in the first place to replace the box controller?

I destroyed my old compressor by running it while the boat was on the hard. When replacing it, I decided to upgrade everything and bought a new mechanical thermostat and speed controller for nominal cost.



You wrote:

"I assume this thermostat was not used previously on an Adler Barbour system?"

No. Brand new Frigoboat thermostat.


You wrote:

"Also when cooling stops was red LED flashing."

No. Just green LED flashing some number of times (sometimes one, two, three, four, five, or six flashes), but the compressor was not running.



Your wrote:

"The speed controller should never be able to stop compressor cooling."

My understanding is that when the thermostat reaches it's target temperature and the switch inside it opens, the green LED turns solid on and the compressor is "idle". When the temperature exceeds the thermostat setting, the switch closes and the green LED starts flashing some number of times indicating the speed at which it is directing the compressor controller to operate the compressor. Am I wrong?

Now that we have the complete story by adding information about compressor was replaced after running refrigeration while boat was out of the water. This then fits into a condition where POE oil traveling through system becomes contained due to compressor overheating oil. This BD variable speed compressor system containing 1/2 the oil of the older fixed speed will not solve the problem.
To replacing only the compressor will not remove all contaminated oil from the rest of the system's components. At this point I assume that is what is your problem. I have promised MJ 360 here with same problem the answer. Its going to be a lone answer so look for it to marrow.

[garyr]

Originally Posted by Richard Kollmann

Now that we have the complete story by adding information about compressor was replaced after running refrigeration while boat was out of the water. This then fits into a condition where POE oil traveling through system becomes contained due to compressor overheating oil. This BD variable speed compressor system containing 1/2 the oil of the older fixed speed will not solve the problem.
To replacing only the compressor will not remove all contaminated oil from the rest of the system's components. At this point I assume that is what is your problem. I have promised MJ 360 here with same problem the answer. Its going to be a lone answer so look for it to marrow.

Richard, The evaporator and filter/dryer were replaced as well. So no contaminants in the system. Also, your theory doesn't explain why the old Smart Speed Controller works, but the new Merlin II's do not.

[Bill O]

Possibly send the Merlin II back for a refund (?) and just use the old smart speed controller.
If you are looking for a digital thermostat controller, you could always set up an inkbird type controller.

[Richard Kollmann]

Originally Posted by garyr

Richard, The evaporator and filter/dryer were replaced as well. So no contaminants in the system. Also, your theory doesn't explain why the old Smart Speed Controller works, but the new Merlin II's do not.

You are assuming the two Merlin are bad and you maybe correct. There may still be material in keel cooler I would use the box speed controller for many hours to confirm merlin's are bad. I would also contact Rob at Frigoboat US in Annapolis he is the expert.

[Pottasch]

I have the exact same problem with the Merlin II. It operates normally until the compressor stops working but the control board acts like it is still functioning normally. It throws no fault codes. coastal climate couldn’t replicate the problem but did send a replacement. It functioned for 2 weeks but now it is malfunctioning too. When I cycle the circuit it operates at about 3.8 to 4 amps and is getting 13+ Volts at the controller.

The stock controller seems to work fine, though I’m told not as efficiently. A real puzzle.

[Nutmeg 42]

Add my name to the list. Fridge works great for a couple of days, then crickets and spoiled food - cycle power and it works again. All new system installed Spring 2022 sourced through Coastal Climate: Frigoboat K35 keel cooled, Coastal Mk3 digital thermostat, Merlin II speed controller.

• Intermittent issue, but common on day 2 or 3 of operation. Power is uninterrupted until I cycle the circuit.
• Compressor stops operating, cool to the touch, no evidence of overheating, etc. Fridge temp climbs to ambient temp of the boat.
• Green operating LED continues to blink as if all is well
• Red fault code LED never lights
• When I cycle the power, the system boots up properly and runs well for another day or two. I’ve not tested it to see if the problem recurs after 2 or 3 days, hesitant to leave the system unattended.

If I remove the Merlin II, the compressor should operate normally at a constant low speed?

garyr and Pottasch: how did this resolve with Coastal Climate? I've sent them an email describing the issue (and linking this post). I'll post back with any updates.

[Pottasch]

Well I’ve given up trying to diagnose the problem, and so has coastal apparently. They said they no longer carry the Merlin and frigoboat is no longer interested in hearing about our struggles. They do offer a full refund but I am cruising and it’s not so easy or cost effective or return it.
While I was still stateside Coastal did have me send the first Merlin in for them to bench test. They were unable to replicate the problem and so they sent a 2nd to me. After 3 days it also did the same thing. I then ran double ought battery cable thinking it may fix the problem (lineloss). It didn’t.
So now I’ve replaced the Merlin with the stock control board set at 2500rpm and it has worked fine for 6 months. I do wish their smart controller functioned as advertised. It would improve efficiency. At this point I think the problem lay with the control module, not the Merlin. Sorry I don’t have better news. It does not seem that many people suffer this problem. Lucky us I guess.

[Anna Sail]

I've just received this response from Coastal Climate Control:

Coastal Climate Control wishes to apologize to all those customers that experienced a problem with their Merlin II compressor speed controllers, and we are sorry for the inconvenience. It has been a very frustrating and trying time for all involved in trying to pin-point the root cause of the issue, and we very much appreciate the help and patience of Alan and other customers who have helped us in our testing program. Coastal has never given up on diagnosing the problem and, together with Veco and the manufacturer of the Merlins, we have been constantly evaluating the feedback from field testing in an effort to replicate the problem. Neither Coastal nor the supplier and manufacturer in Italy have been able to replicate the problem no matter what testing routines we tried, so the help and input from customers has been vitally important. The more feedback we've received from the field, the closer we have come to a resolution, but until we have a proven replacement, we have no choice but to halt the import and sale of this item. Today I have been informed by the manufacturer that they have now been able to replicate the problem after analyzing the latest field-test reports, and that a fix has already been applied and that it has passed rigorous testing in the lab. I have no further details, but it is certainly not a design flaw, and similar issues have surfaced previously when an electronic component manufacturer changed the specifications and/or tolerances of an item without informing the equipment manufacturer. With this news we are reasonably optimistic that a reliable solution is not far away, but we need to field-test this new version Merlin to be sure of its reliability, and that will be happening very soon.

[Pottasch]

I would like to add, in case there is any misunderstanding, Coastal has been very responsive. I did not mean to imply otherwise. I will be waiting with baited breath the potential fix. Best.